DSpace Collection:

Equidade digital na educação pós-pandemia: mediação pedagógica com plataformas digitais para o ensino de eletroquímica em contextos educacionais diversos

Wed, 12 Aug 2026 00:00:00 GMT

Title: Equidade digital na educação pós-pandemia: mediação pedagógica com plataformas digitais para o ensino de eletroquímica em contextos educacionais diversos Abstract: Electrochemistry presents notorious and well-documented teaching and learning difficulties, which were substantially aggravated by the implementation of emergency remote teaching. This context demanded greater student autonomy and required educators to develop effective didactic alternatives for conceptual mediation at a distance, thereby deepening long-standing obstacles. This qualitative investigation aimed to evaluate the impacts of implementing digital educational resources—an offline application and a website titled Electrochemistry in Everyday Life—on the teaching and learning process. The goal was to overcome historical obstacles exacerbated by the remote context and promote equity in access to meaningful learning across distinct educational settings (public, private, and rural) in Itumbiara, Goiás, Brazil. The study unfolded sequentially in five methodological stages: first, a systematic literature review was conducted to map obstacles in electrochemistry education and analyze the effectiveness of active methodologies; subsequently, the challenges of emergency remote teaching in Science/Chemistry were investigated through the perceptions of teachers and students from three educational contexts, which were contrasted with institutional documents; third, after development and classroom implementation, the digital resources underwent rigorous validation by teachers and students (focusing on usability, user experience, and learning principles), resulting in an improved version and demonstrating feasibility even in contexts with limited technological infrastructure; finally, the impacts of these resources on student participation and cognitive performance were evaluated using pre- and post-intervention questionnaires across the three contexts. Initial diagnostic results confirmed the severity of the situation, with 63% of students rating their remote Chemistry classes negatively and citing a lack of concentration at home as the primary hindrance. These challenges were most pronounced in the Rural School, which exhibited a significant lack of teacher training and technical support. Following the intervention with the digital tools, quantitative data showed significant progress, noting a considerable improvement in conceptual understanding—exemplified by the Public School achieving approximately 50% correct answers in a Moodle Quiz—indicating the overcoming of cognitive obstacles. Qualitatively, students reported increased motivation and a clearer grasp of abstract concepts, attributing this progress to the resources' effective contextualization of content with everyday phenomena. Nevertheless, difficulties associated with prior curricular gaps persisted in the Rural School, despite these students showing notable engagement in practical activities. In conclusion, the complexity of challenges inherent to remote teaching, which manifest heterogeneously, tends to intensify pre-existing educational disparities. However, the developed digital resources, designed with a contextualized approach and subjected to a rigorous validation process, represent promising pedagogical strategies for mitigating learning gaps in electrochemistry. These tools demonstrated potential to catalyze student engagement, foster autonomy, and outline feasible pathways for promoting educational equity in diverse contexts, particularly in scenarios with infrastructural limitations. The research's legacy points toward transforming an emergency experience into lasting progress through continuous investment in evidence-based digital resources and teacher training for critical implementation.

Desenvolvimento de plataformas analíticas portáteis baseados em línguas optoeletrônicas e narizes eletrônicos para análise discriminativa

Mon, 27 Jul 2026 00:00:00 GMT

Title: Desenvolvimento de plataformas analíticas portáteis baseados em línguas optoeletrônicas e narizes eletrônicos para análise discriminativa Abstract: Artificial olfactory systems have been widely employed for the detection and discrimination of chemical compounds in various analytical applications, including quality control, environmental monitoring, diagnosis, and food analysis. However, their performance remains limited by high instrumental cost and constraints in the generation and processing of chemical information. In colorimetric systems, limitations in signal acquisition may reduce response resolution and hinder the discrimination of complex samples. In this context, the development of low-cost and more efficient approaches for chemical information extraction remains highly relevant in Analytical Chemistry. This thesis aimed to develop and evaluate two artificial olfactory systems based on a portable electronic nose and a paper-based colorimetric sensor array with multichannel signal acquisition, integrated with chemometric tools for chemical pattern recognition. The low-cost electronic nose was constructed using semiconductor sensors coupled to an open-source microcontroller platform, while the colorimetric system employed a paper-based sensor array combined with an AS7341 spectral sensor. In both cases, optimization of experimental conditions led to more stable and reproducible responses. The electronic nose enabled the separation of volatile organic compounds, whereas the colorimetric sensor array allowed the discrimination of acid–base systems and eleven types of food samples. Compared with RGB-based approaches, the multichannel system exhibited higher resolution, sensitivity, and robustness against experimental interferences. PCA and HCA confirmed the presence of multivariate chemical signatures capable of discriminating complex systems. Overall, the results demonstrate that both approaches are promising low-cost analytical tools for screening and quality control. Future work includes extension to different matrices and integration with machine learning methods to improve classification and predictive performance

Eletrodos baseados em grafeno obtidos por gravação a laser: eletroanálise de amostras ambientais, biológicas e de alimento

Fri, 31 Jul 2026 00:00:00 GMT

Title: Eletrodos baseados em grafeno obtidos por gravação a laser: eletroanálise de amostras ambientais, biológicas e de alimento Abstract: Laser engraving has emerged as a promising technique for the rapid, simple, and low-cost fabrication of electrochemical sensors. In this thesis, laser-induced graphene (LIG) electrodes were fabricated through the direct engraving of polyimide using a CO₂ laser, aiming at the development of electrochemical methods for applications in food, environmental, and biological samples. To achieve this goal, the work was conducted in three stages. Initially, using unmodified LIG electrodes, a method was developed for the determination of total antioxidant capacity (TAC) in tea samples through the quantification of the consumption of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, employing batch injection analysis (BIA) with amperometric detection. The method exhibited a linear range from 2 to 900 μmol L⁻¹, a limit of detection (LOD) of 0.6 μmol L⁻¹, and high precision (relative standard deviation, RSD < 4.0%). The TAC of the samples followed the order: mixed tea < black tea < green tea < green tea with hibiscus, in agreement with the conventional spectrophotometric method. In a second stage, the applicability of these unmodified devices was extended to the determination of chloramphenicol in honey samples by adsorptive stripping differential pulse voltammetry (AdSDPV). This method showed linearity in the range of 10 to 160 μmol L⁻¹, an LOD of 1.0 μmol L⁻¹, and recovery values ranging from 86% to 109%. Finally, it was demonstrated, for the first time, that the application of only 3.0 μL of dimethyl sulfoxide (DMSO) onto the surface of LIG electrodes significantly enhances the electrochemical activity of the material. Physicochemical and electrochemical characterizations revealed changes in the chemical composition, structure, and surface morphology of LIG, including an increased concentration of oxygen-containing functional groups, structural reorganization favoring the formation of graphitic domains, enhanced hydrophilicity, increased surface roughness, and reduced charge-transfer resistance. Based on this surface modification strategy, a method was developed for the determination of sulfanilamide in water and synthetic urine samples using differential pulse cathodic stripping voltammetry (DPCSV). The method exhibited a linear response in the range of 0.3 to 9.0 μmol L⁻¹, an LOD of 0.09 μmol L⁻¹, and recovery values ranging from 90% to 104%. Overall, the results demonstrate that LIG-based electrodes constitute a versatile, efficient, and low-cost analytical platform. Furthermore, surface treatment with DMSO proved to be a simple and effective strategy for enhancing the electrochemical performance of LIG, thereby expanding its potential for the development of electrochemical sensors.

Estudos in silico da proteína TcP21 no contexto da doença de Chagas

Mon, 27 Jul 2026 00:00:00 GMT

Title: Estudos in silico da proteína TcP21 no contexto da doença de Chagas Abstract: Chagas disease, caused by Trypanosoma cruzi, remains a significant public health concern, with still limited therapeutic options. In this context, the TcP21 protein, secreted by extracellular amastigote forms, has emerged as a molecular target of interest, involved in alternative and still poorly explored infection pathways. This thesis aimed to characterize TcP21 in silico from two complementary perspectives: the identification and characterization of binding sites on its surface, and the elucidation of potential interaction interfaces in the TcP21–CXCR4 complex. The integration of mixed-solvent molecular dynamics simulations, fragment-based molecular docking, and pharmacophore-based molecular docking followed by molecular dynamics, driven by occupancy-based volumetric maps, enabled the convergent identification of a binding site on TcP21. This site involved the key residues GLU55, ASP52, VAL70, ILE62, and TRP77. The observed interactions, including salt bridges, hydrogen bonds, charge–charge interactions, and π–alkyl contacts, formed an intermolecular network consistent with the recognition of protonated amino, acetamido, and phenyl functional groups. Binding modes of the TcP21–CXCR4 complex were generated by molecular docking and subsequently refined through multireplica molecular dynamics simulations in a biomimetic environment. Consensus analysis of the trajectories, based on a ΔSASA-driven multimetric scoring function and on the evaluation of intermolecular contacts (number, frequency, and temporal stability), revealed a continuous segment in TcP21 (LYS23–PHE39) with typical protein–protein interface properties. In CXCR4, the transmembrane domains TM5, TM6, and TM7 formed a stabilized structural core within the extracellular vestibule, whereas regions such as ECL2 and the N-terminal domain exhibited greater conformational flexibility. The resulting interface displayed a modular organization, predominantly stabilized by van der Waals interactions, with additional electrostatic and polar contributions conferring directional specificity to the molecular recognition process. The integrated analysis of the studies indicated the presence of two functionally specialized regions in TcP21, potentially associated with pharmacophore ligand binding and host receptor recognition, respectively